If you are noticing a weed with bright yellow flowers in lawns now, it may very well not be dandelion (which is generally not in bloom right now) or black medic. In fact, there is a good chance that it is Birdsfoot trefoil (Lotus corniculata). Birdsfoot trefoil has long been used as a pasture crop and is known to be able to escape from its intended site. But it is only in the last decade that it has become increasingly visible in managed turfgrass - first in waste areas and abandoned fields, then parks and roadsides, and now residential lawns.

The dew point temperature is an important environmental measurement from both an agronomic and worker health in turf management. The dew point is the temperature at which water vapor in the atmosphere will condense forming dew. So when the dew point temperature is high, for example at 72 F, dew forms at or below 72 F. Thus, the higher the dew point, the greater amount of moisture in the air. High dew points indicated high humidity so when the dew point remains high the turf remains relatively wet, which is conducive to a host of problems including diseases. For workers a dew point temperature above 68 F is uncomfortable, while dew points above 75 F are oppressive.